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and today lemurs are found only in Madagas-
car. Free from the competition that likely drove
them to extinction elsewhere, they evolved into
richly varied forms, including now vanished
species that were big as gorillas and the palm-
size mouse lemur, the smallest living primate.
e tsingy also provides refuge on a smaller
scale. Protected by walls of stone and wet by
seasonal rains, the forest within is very di er-
ent from the palm savanna curling around it
to the east and the coastal areas that ank it to
the west. It is a relict of another era, when for-
est corridors might have linked one side of the
island with the other.
In recent millennia a natural drying trend
fractured those corridors. en came people.
Since the rst humans arrived in Madagascar
some 2,300 years ago, nearly 90 percent of the
island s original habitat has been destroyed, most
of it harvested for timber or felled or burned to
create room for crops and, more recently, cattle.
As a result, many of the species that lived on the
island are thought to have gone extinct.
In the west the tsingy walls in a large por-
tion of forest. e stone serves as a barrier to
human settlement and to cattle, which threaten
wildlife habitat all across Africa with their plod-
ding hooves and insatiable appetites. e tsingy
also acts as a rebreak, shielding the forest from
res---both natural and those set by humans.
"Bemaraha has unusual animal and plant
populations in part because the surrounding
area has been changed, either by humans or by
climate change," said Brian Fisher, curator of
entomology at the California Academy of Sci-
ences. "We ve found it s much more diverse than
we initially thought."
Rakotondravony
and I hiked into a tangled forest lining the oor
of a grike. We paused at a large ant mound, red
ants streaming from the earth. e air around
us was damp, smelling of wet basements, and
from within the canyon and the forest, a rhythm
hung in that thick air, somewhere between
heard and felt---the incessant buzzing of a
billion insect wings.
Rakotondravony poked gently into the
mound, looking for a renivitsika, or ant mother,
a kind of snake that o en lives within a colony s
dark interior. We found no snakes, but scan-
ning the area near the mound, Rakotondravony
pointed to several plants, including palmlike
trees with slender fronds. ese, he explained,
were another kind of guest that had made an
unlikely home in the tsingy s narrow passages.
ey were a species common in the wet forests
of eastern Madagascar but mostly absent from
the much drier west. Only here, within the
grikes, had the plants escaped the drying sun
and roaming wild res. e plants were just one
example. ere are certain frogs too, he said,
whose nearest known relatives live hundreds of
miles away in the eastern forests.
e di cult terrain creates still tinier refuges,
where some creatures appear to have evolved in
greater solitude, restricted to just a few canyons
within the tsingy. John Cleese s lemur, a mouse
lemur, and at least two of the pinkie-size dwarf
chameleons---some of the world s smallest---illus-
trate this kind of micro-endemism, where evolu-
tion has tailor- tted animals into tight niches.
Brian Fisher has traveled to the region three
times to understand how these refuges formed
and how they have shaped the life within them.
rough DNA analysis, he is comparing ants
from the tsingy region to ants in eastern Mada-
gascar, hoping to pin down exactly when the
ants, and the forests, became isolated. The
results will provide clues to how animals evolve
once they are shut o from other populations,
and whether they respond to climate change
only by retreating into refuges or by develop-
ing new traits as well. e answers, Fisher said,
could have implications for the future, as human
activity undermines habitats and the planet s cli-
mate changes.
Because it is remote and virtually impenetra-
ble, development seems less likely to threaten
the tsingy ecosystem than would a shift in
regional weather. Lower humidity, less rainfall,
increased acidity in the rain---any of these might
harm the forests, even the stone itself.
"I wonder how long they could survive, these